[clang] [clang][analyzer] Model more getline/getdelim pre and postconditions (PR #83027)

[Balázs Kéri via cfe-commits]

https://github.com/balazske commented:

This functionality could be added to this checker, but to `StdLibraryFunctionsChecker` too, and probably will be added at a time (summary of `getdelim` is not accurate now in that checker). The same bug condition is checked by two different checkers in that case. Otherwise I prefer to add such checks (for NULL arguments) to `StdLibraryFunctionsChecker`.

https://github.com/llvm/llvm-project/pull/83027